Senior Labour MPs rejected Mr Corbyn's plea to rally behind them if he defeats his challenger Owen Smith in the September leadership election.

He said: "If this parliament runs to full term, then the new boundaries will be the basis on which elections take place".

"In that case, there will be a full selection process with every constituency".

The Saving Labour campaign urged those opposed to Mr Corbyn's leadership to sign up as registered supporters, saying: "Britain and Labour needs new, strong leadership for the months ahead".

May relentlessly mocked opposition Labour leader Jeremy Corbyn, a veteran socialist who is facing a leadership challenge backed by dozens of his own MPs, using his own questions against him.

But in an indication of the scale of division within the Labour ranks, a total of 162 of the party's MPs - some 70% of its representation in the Commons - nominated Mr Smith for the leadership, along with half of Labour's MEPs.

'There is a huge amount of talent on the Labour benches.

If the same numbers turn out this year, it means that the selection of Labour's new leader could be decided by more than 643,000 voters.

Declaring that he had the ability to conveniently forget unpleasant things said about him by MPs, Corbyn said: "Because, come September, when this election is done and dusted, there will still be a Tory government in office, there will still be grotesque levels of inequality in our society, there will still be whole parts of this country that are left behind".

"It's the job, it's the duty, it's the responsibility of every Labour MP to get behind the party", Corbyn said at the start of his leadership campaign.

Jack Dromey, Labour MP for Birmingham Erdington, said Mr Smith was a Labour MP in the tradition of Aneurin Bevan, who helped create the NHS.

MPs were "part of, but not the entirety, of the Labour party", Corbyn said, referring to his popularity among members. They told The Independent they are prepared to trigger another leadership election next year - and even a further contest the following year.

In an echo of the five "giant evils" identified by William Beveridge in the 1940s, Mr Corbyn will say: 'Today what is holding people back above all are inequality, neglect, insecurity, prejudice and discrimination.

He also announced he would require all firms with more than 21 staff to publish audits of pay to see if women and ethnic minorities were lagging behind other employees.

'I hope they will recognise that and come on board'.

'In my campaign I want to confront all five of those ills head on, setting out not only how Labour will campaign against these injustices in opposition but also spelling out some of the measures the next Labour government will take to overcome them'. The majority of Labour lawmakers have voted to say they don't have confidence in his leadership, but Corbyn has said he has no intention of resigning, arguing that he has the overwhelming support of Labour members.